Telephone-exchange system.



No. 766,450. iPATENTED AUG. 2, 1904. I. KITSEE.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED NOV. 23, 1900.

4 SHEETSv-SHBET 1.

NO MODEL.

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11W/@5565 y e No. 766,450. PATENTED AUG. 2, 1904. I. KITSEE.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED NOV. 23. 1000.

4 SHEETS-SHEET 2.

N0 MODEL.

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No. 766,450. PATENTED AUG. 2, 1904.

I. KITSEE. TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED NOV. 23, 1900. NO MODEL. 4 SHEETS-SHEET 3.

No. 766,450. PATENTED AUG. 2, 1904. I. KITSBE.

TELEPHNE EXCHANGE SYSTEM.

APPLICATION FILED NOV. 23, 1900. NO MODEL. v 4 SHEETS-SHEET 4.

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IPM/655625' UNITED STATES Patented August 2, 1904.

PATENT EEICE.

TELEPHONE-EXCHANGE SYSTEM.

SPECIFICATION forming part of Letters Patent No. 766,450, dated August 2, 1904.

Application filed November 23, 1900. Serial No. 37,501. (No model.)

T0 @ZZ whom nfl/(ty concern.'

.Be it known that I, IsIDon KrrsEE, of the city and county of Philadelphia and State of Pennsylvania, have invented certain new and useful Improvements in Telephone-Exchange Systems, of which the following' is a specilication.

My invention relates to an improvement in telephone systems, and has more special reference to the devices employed in the central station and the arrangements of same.

The objects of my invention are to simplify the operations in the central station, as well as to facilitate the operators work in detecting the status of the different circuits leading' into the central station.

To this end my invention consists in the features and arrangements, as will hereinafter be described, illustrated in the drawings, and more specially pointed out in the claims following' the specification.

I am well aware that some of the features and arrangements as described in this speciiication can be employed in systems already in use without necessitating' the employment of all the features of this invention and thereby changing entirely the method of to-day; but to organize a telephonie system wherein the operations in the central station are reduced to a. minimum and the status of the different circuits is to be detected by the operator at a glance it is necessary to malte use of all the devices and arrangements as herein described. Therefore the arrangements and devices as herein described form in one sense one integral unit, notwithstanding that part of the same can be employed independently of the other parts.

Referring to the drawings, Figure l is a plan view of a portion of one corner of the switchboard, showing'four plugs in place. Fig. 2 is a vertical sectionthrough two holes of theswitchboard, showing two plugs inserted therein, the plugs being in section, showing the inner parts thereof. Fig. 3 is a vertical section of the lower portion of one of the plugs, showing the electromagnetic device in its normal position. Fig'. et is a plan view of a-portion of the switchboard, showing the conductingplates arranged in a manner so that each layer shall consist of three different series. Fig'. 5 is a cross-section of part of one of the plugs as illustrated in Fig'. 3. Fig. 6 is a cross-section of part of the other plug as illustrated in Fig. 3. Fig. 7 isa diagrammatical View of two subscribers circuits, one calling and one at rest. Fig. 8 is a similar view as Fig'. 7, the central station in connection with subscriber No. l. Fig. t) isa similar view as Fig'. T and Fig. 8, subscriber No. l being' in connection with the central station and subscriber No. 2 called up. Fig'. l0 is a similar view to Figs. T, 8, and t) in which both subscriber No. l and No. are connected for intercommunication. Fig'. ll is a diagrammatieal view of the arrangement of the switchboards and the light-board. Fig. 1Q is a side elevation of Fig'. ll, showing the light-board in section.

l will lirst describe the s\\'itchboard located at the central station and the switchplug' to be used in connection with this switchboard. The switchboard (designated in the drawings by the letter S) consists of the nonconducting face-plate Si, a series of conducting-plates divided by non-conducting supports and numbered from l to "9, re-

spectively, and a non-conducting rear plate S". This switchboard is provided with the holes or perforations S, the numbers of the holes corresponding' with the numbers of the circuits designed to be connected to the contact plates or springs at or near these holes. To the face-plate are secured around the periphery of each hole the contact-plates fc', af, w, wf, and w. '.lo the rear plate are secured two pairs of contact-springs (designated each by the letters f and ff) for each of the holes with which said plate is provided. The construction of this switchboard is shown in Fig'. 2, of which Fig. l is a modilication. .In Fig'. 2 each plate extends the whole length and width ot the board; but in Fig. 4 the plate is cut up in strips. These strips are secured to the non-conducting' support for the purpose of saving' space on the switchboard and saving length in the s\\f'itchplug, as will hereinafter be more fully described. Instead of each layer consisting' of three series of contact-strips, as illustrated in Fig'. -l. each layer may consist of any number of strips desired.

IOO

, There are two series of switch-plugs, series t and series a. The switch-plugs of series a are used for the circuit which is calling, and the switch-plugs of series d are used for the circuit to be called up. In other words, if a circuit is calling, then the operator selects a plug of the series t and inserts the same in the hole of the respective circuit, and if the operator wants to call up a subscriber he selects a plug of the series a' and inserts the same in the hole of its respective circuit. As illustrated in Fig. l, each plug is provided with a letter, the letters of one series corresponding with the letters of the other series. We therefore have plug A of the series t and plug A of the series a. Each of these plugs is provided with contact-points arranged in a manner so that if a plug is inserted in one of the switchboard-holes this plug will make an electrical connection between one of the springs at the rear of the switchboard and one of the conducting-plates located between the face-plate and the rear plate; but the location of the contact on the plugs differs in a manner, so that the plug of one letter will connect the spring with one of the plates andthe plug of a second letter will connect the spring with another of the plates. Each plug is provided with a lamp f and the glass plate f This glass plate f' is provided with the letter A or B or C, as the case may be; but to distinguish series a from series a' the lettering or the glass plate of one series is colored differently vfrom the lettering or glass plate ofthe other series, so, also, can the whole plug of one series be colored red, for

Ainstance, and the whole plug of the other series be colored white. Each plug is also provided as to its inner space with an electromagnetic device `consisting of the electromagnet b and the armature c, kept downward with the aid of the spring c2. This armature is provided with the bell-crank c', in juxtaposition vto which is the spring c3 and the push button ci. The manipulation and operation of this electromagnetic device is as follows: Normally the spring 02 presses the armature downward, and the position of the spring-hook c3 is out of contact with the bell-crank c; but when-the plug is inserted in one of the holes the hook-spring 03 is pressed toward and in contact with the bell-crank c with the aid of the .push-button 0*. If 4now the electromagnet b is energized-.and the armature drawn upward toward the core of this electromagnet, then the hook end of the spring ci catches in the bell-crank c, and if the circuit magnetizing the core is broken the armature will not be able to again resume its former position, because vthe bell-crank will be kept in place with the aid of the hook-spring. The

the contact-springs c.

purpose of intercommunication, as illustrated in Figs. 7, 8, 9, and l0. In these'illustrations I omitted entirely all the transmitting instruments and connections of the receiving instruments, with the exception of the transmitter itself and the alarm device, as these devices are necessary to illustrate my invention and the omitted devices do not form part of the improvements as set forth in this application.

In Fig. 7 subscriber No. l is calling up the central and subscriber No. 2 is at rest. I take the circuit of station No. 2 as an example to illustrate the wiring and connection of all the subscribers stations as long as their circuits are not in use. Each of the circuits consists of two legs, (designated for station N o. 2 by the characters 2 and 2b.) The leg 2a is normally at the subscribers station not connected with the leg 2b and is at the central station connected to one terminal of the lamp or other annunciating device h2. This lamp forms part f of the light-board, as illustrated in Figs. 11 and l2. In this board the different lamps are numbered and correspond in number to the numbers of the circuits to which they are attached. The other terminal of the lamp h2 is connectedgwith the spring-contact e in electrical connection with the spring-contact e. These spring-contacts are secured to the switchboard S, as illustrated -in Fig. 2. From the contact e the circuit connects with the lamp 2. This lamp forms part of the annunciating device for the operator, and from the lamp the circuit is carried to the positive pole of the common source of electricity m. At the subscribers station the second leg-that is, the leg 2b-is normally connected with the lever on which the receiver rests. Through the weight of this receiver the lever is pressed against the lower contact-point, which contact-point is in electrical connection with one terminal of the alarm device g, the other terminal of which is grounded at g. In the central station the circuit 2b is connected with a second contactspring e, also in electrical connection with This pair of contactsprings is also secured to the switchboard S. From this pair of contact-springs the circuit is carried tothe negative pole of the common source of electricity on. It will therefore be seen that the subscribers circuit, if perfectly at rest, is connected at the central station first to the source of light of the-light-board `and then through a contact-spring with a source of light at the operators desk, then to a source of electricity, from this source to a pair of contact-springs, from whence it returns to the subscribers station. Station No. l is illustrated, as said before, as calling. The subscriber at this station has removed the receiver from the hook, Vand the lever relieved of its weight breaks its connection with the lower contact-point and makes its connection with the upper contact-point, and thereby IOO IIO

connects both legs of the circuit, which legs are designated by the characters l and lb, respectively. Through the connection of these two leg's the circuit leading' from the battery fm., which is normally open, is now closed, and the How of the battery will be fromm through i", d, i, L, circuit-leg l, through lever to circuit-leg l", spring-contact e, spring-contact @l to the negative pole of said battery. The lamps /t/ and /f/ will therefore glow. The function of the lamp It will later on be more fully described, and the function of the lamp y/ is to notify the desk operator that the circuit to which said lamp is attached is calling. Let it be supposed that leach operator has in charge three hundred circuits and that the operator to which the circuits of stations No. land N o. 2 are assigned has the circuits from one to three hundred in charge. The desk is provided with three hundred lamps or similar annunciating devices, each lamp carrying the number corresponding to the number of the circuit to which it is attached. In the case as illustrated the lamp 'f of circuit No. l will glow. As soon as the operator is thereby notified that subscriber No. 1 is calling he will take one of the calling-plugs described above and will insert the same in the hole in the switchboard designated by the number corresponding tothe number of the lamp. The insertion of this plug will accomplish the following: It will break the electrical connection of contact-springs e e', connected to the circuit-leg l, and will break the electrical connection of e e, connected to the circuit-leg l, thereby entirely disconnecting the common source of electricity m from the circuit of station No. l; but at the same time it will connect contact e of leg l, through lamp and contact in with the positive pole of the battery lc, and itwill connect contact-spring e of leg lb, through armature c of electromagnet I), contact-point w", contact-point fc3, with one terminal of the operators phone j, the other terminal of which is connected, through resistance j', with the negative pole of the battery rlhe circuit therefore of station No. l with the common source of electricity m is entirely broken and established with the battery It', including the operators phone y'. The flow of the current of this circuit will therefore be i from the positive pole of the battery through contact :112, lamp f, contact-spring e, lamp It', circuit-leg l, lever, and circuit-leg l, springcontact e, armature c, contact rc3, operators i phone j, resistance j', back to the negative 1 pole of the battery. From this arrangement it will be noticed that as soon as the callingplug is inserted in the hole of the switchboard corresponding with the number of the callingcircuit the operators light corresponding with this circuit is extinguished; but the lamp of the light-board still remains connected and glowing'. At the same time the new connection includes the operators phone, and the opl erator is thereby enabled to ask subscriber No. l with whom he wishes to be connected.

It is taken for granted that the calling-plug inserted in circuit N o. l is designated by the letter A and is designed to connect the conducting -plate l with the calling' circuit. The insertion of this plug will therefore, in addition to the connections enumerated, connect the conducting-plate I through contact :118, coil of the electromagnet b, armature c with contact-spring' @of leg ll. This state of the circuit is illustrated in Fig. 8, in which iigure station No. 2 is still at rest. Subscriber No. l imparts now to the operator his desire to be connected to No. 2. The operator takes a plug of series a or circuit to be called corresponding in letter to the plug already inserted in the calling-circuit, which in this case is letter "A,and inserts the same in the hole of the circuit of station No. 2. The insertion of this plug will accomplish the following results: It will break the electrical connection of contact-springs c e', connected to the circuit-leg 2, and will break the electrical connection of e e', connected to the circuit-leg 2b, thereby entirely disconnecting the common source of electricity m from the circuit of station No. 2. At the same time it will connect the contact e of leg 2n through contact m* with the negative pole of the battery lv, and it will connect the contact-spring e of the leg 2" through lamp f, armature c, contact m, contact fr with the positive pole of the battery Z, the negative pole of which is grounded at l. It will also at one and the same time connect the spring-contact e of leg 2l4 through lamp f, armature c, coil of electromagnet contact 08 with the conducting-plate l. It will also at the same time connect, through contact afs, connecting part c* of armature c, contact sul, contacta?, the conducting-plate Z, with the negative pole of the battery t", the positive pole of which is connected with the positive pole of the battery it'. As long as subscriber No. 2 does not respond-that is, as long as subscriber No. 2 does not connect at his station leg 2L with leg' 2"-the circuit connection of this circuit with the battery 7c is not completed and does not in the least alter the connection of this battery with circuit No. l; but the insertion of this plug' connects the leg 2b, normally grounded at the subscribers station, at g, through the alarm g, with the grounded source of electricity Z, grounded at thereby completing a circuit -including the battery l, contact fc', contact w", armature c, lamp j', spring-contact e, leg 2"` alarm g, ground g/ and l. The alarm, therefore, of No. 2 will be actuated, and as long as the lever will rest on the lower contact-point the bell, if the alarm is such, will ring. At the same time the light of the lamp f will light intermittently if the alarm includes a makeand-break device, as is usually the case in alarm-bells. At the same time a circuit is es- IOO IIO

Vtablished 'as follows: from the mutual contact-point of the positive poles of the batteries and lo through m2, lamp f, springcontact e of leg l, lamp 7L', circuit-leg l, le-

, ver, circuit-leg lb, spring e, connected to said ing part ciof armature c, contactarlo, contact m9, and negative pole of battery It. Through the iiowl of the current in this circuit the electromagnet of the plug of the calling-circuit will be energized, and the armature c will be pulled toward fthe core of the electromagnet and away from the contact x5, thereby breaking lthe circuit which includes the operators phone. .The insertion of the plug in the hole of the circuit to be called serves, therefore, two purposes: First, it rings up the subscriber to be called, and, second, it disconnects the operators phone from the callingcircuit. rILhis status o'f the two circuits is'shown in Fig. 9.

As soon as subscriber No. 2 in answering removes the receiver from the hook the followingchanges'are made in the circuits: First, the circuitincluding the battery k is completed inthe following manner: from the positive pole of this battery to contact m2, lam-p f, spring e of circuit-legi, lamp k', 'leg la, lever, leg 1b, contact c, armature c, coil of electromagnet b, `contact m8, conducting-plate Z, contact m8 of the plug of the circuit to be called, coil of electromagnet I), lamp f, spring e of leg 2b, leg 2b, lever, leg 2, lamp spring e, contact mi, back to the negative pole of the battery 7c. Through the flow of the current in this circuit the coil of the electromagnet b in theplug connected now to the circuit to be called will be energized, and the armature c of this plug will be ldrawn upward and away from the contacts and mw, thereby breaking the circuit including the grounded battery Z and 'the circuit including the battery 7c. The only source of electricity, therefore, remaining in the circuit will be the battery It. No part of the circuit is-connected to the ground, and both subscribers are at liberty to communicate. As long as both parties are in communication the lamps in both plugs will glow, and so will the lamps of both circuits in the light-board; but as soon as one or the other of the subscribers stops communication by replacing the receiver on the hook the circuit of the battery is broken; but the circuits of the other batteries which were formerly established cannot be restablished on account of the catching device of the electromagnet before described. The lamps, therefore,o't` both plugs, as well as the lamps of the light-board, will be extinguished, thereby notifying the operator that the respective circuits are again at rest. From this description it will be seen that, first, if all the circuits are atrest all the lamps at the light-board,

as well as all the lamps at the desk, will remain unlighted; second, as soon as a subscriber removes his receiver the respective lamp at the light-board and the respective lamp at the operators desk lights; third, as soon as the operator places the plug in the calling-circuit the desk-lamp is extinguished, but the lamp in the light-board remains lighted and at the same time the lamp in the plug lights; fourth, the insertion of the plug in the calling-circuit connects the operators phone with said circuit; fifth, as soon as the operator has inserted the second plugin the circuit to be called up theoperators phone is Yautomatically disconnected from the circuit calling; sixth, the light of the plug for the cal-lingcircuit will remain lighted, and-the light of the plug for the circuit to be called will give an intermittent light as 'long as -the subscriber called up does not answer; seventh, as soon as the subscriber called up vanswers the lamp in both plugs will lightcontinuously; eighth, the lamps in the light-'board of both circuits, calling and called up, will light; ninth, as soon as one of the subscribers, either the calling or being called up, replaces his receiver on the hook the lights in the plugs, as well as the lights in the light-board, are extinguished.

With the exception of the insertion of the two plugs all other operations, connections, and disconnections are automatic.

In Figs. ll and 12, where the arrangement of the desk-lights, switchboards, and lightboard is shown, S represents the switchboard; c', the desk-lights; H, the light-board; it, the lamps in said light-board; H', the magnifying-glass in said light-board.

I will now describe the lgeneral arrangementand, where necessary, the particular Vreason for such arrangement premising that IOO modifications may be made in respect as to the precise number and space of parts described.

It is lsupposed for the sake of illustration that the devices and arrangements as herein set forth are to be applied to a telephonic exchange consisting of six thousand subscribers. The circuits leading from these subscribers are, as usual, carried through the subterranean parts of the exchange and there provided with the usual lightning-arresters.

In the exchange or operating room proper the following arrangement shall be carried out: In about the middle of the room is placed a superstructure about tive feet high. On this l superstructure is placed the light-board. This board is preferably made of wood and is provided with six thousand holes or perforations, not counting the holes or perforations necessary for trunk-lines connecting this exchange with a second or third exchange, and which trunk-lines or their connections will not be described in this specification. In each of the perforations is placed a small lamp in a manner so that the light ofthe lampiseasilydising' the number of the circuit which is connected to the lamp.

The exchang'e or operating room is also provided with a series of y circuit No. 10, and this plug has a contact twenty desks, arranged as follows: three;

desks for the operators-in our case with light-board, facing' the same and standing' about a foot or foot and a half above the floor;

four additional desks on each side of the lightboard, also facing' the same and standing' about three feet from the iioor. rlhe operator at each one of the desks will be placed in charge of three hundred circuits and will have at his disposal one switchboard, one desk-annunciator, and a number of plugs of both series.

It is a fact verified by experience of many years that not more than from six to ten per cent. of the subscribers are at one and the same time in intercommunication with each other, or, in other words, at one and the same timeonly ten per cent. of the circuits convergingin the exchange are in actual use. An

operator therefore having in charge three i hundred circuits will only have connected simultaneousl, at the utmost on his switchboard from twenty to thirty subscribers.

The l switchboard foreach operator is provided bewhole area of the board and having' pcrforations coinciding' with the perforations in the board proper, as is illustrated in Fig. Q. These conducting-plates are designed to take the place of the cords usually employed in connecting' two subscribers stations for the purpose of intercommunication. The number of these conducting-plates has to depend on the number of circuits of which the operator has to take charge, and taking' into consideration the fact that only ten per cent. of the subscribers circuits are simultaneously in use the number of conducting-plates with which each switchboard is provided need only be ten per cent. of the number of circuits of which the operator has charg'e and, as in our case, each operator is assigned three hundred subscribers it follows that the switchboard for each operator needs to have no more than from twenty to thirty of these conducting-plates.

From what has been said the ofiice of the conducting-plates is quite apparent; but the following' illustration will make their use more clear: supposing' that circuit No. S

should be connected on the switchboard to circuit No. l0, to connect these two circuits together in a manner as practiced to-day one terminal of a connecting-cord is inserted in the jack of circuit No. 8, and the second tei'- minal of the same cord is inserted in the jack of circuit No. 10. W'th the arrangment of stationary conducting plates behind the switchboard the cord is unnecessary, for the reason that if one plug' is inserted in the hole of No. S, and this plugl has a contact connecting the circuit No. 8 to a certain conductingplate, and a plug' is inserted in the hole of connecting the circuit No. 10 to the saine conducting-plate as the lirst plug has connected circuit No. 8 it follows that both circuits are connected together and that the conducting'- plates of my arrangement perform the ofiice of the connecting-cords usually employed.

Every operator will have at his desk, first, three hundred annunciating' devices, provided with the number of the circuit to which it is connected; second, a switchboard consisting' ofthe board proper and,say, thirty conducting'- plates normallyY out of contact with any of the circuits; third, a number of plugs for the purpose of connecting the circuits. lt is necessary here to give, more in detail the office and arrangement of the plugs. I will first state that it was 'found in practice that to avoid all interference between one circuit and the other and to lessen the noise it is best to disconnect entirely the circuits to be connected for the purpose of intercommunication from their common source of electricity, to which they are normally connected. To accomplish this object automatically, l have provided each plug' with wedge-shaped terminals in a manner so that the insertion of the plug' in the hole should break the connection between that part of the circuit which enters the exehang'e and that part of the circuit which is connected to the common source of electricity.

As said above, I have entirely dispensed with the connecting-cords and have substi- IIO tuted therefor stationary conducting-plates, and I have shown that with the aid of plug's these stationary conducting'- plates can be brought in Contact with the terminals of two circuits, thereby connecting' these circuits in 115 series; but let us suppose that circuit No. 8 is already connected to circuit No. l() and that now the connection of two other circuits has to be made. It is apparent that one conducting-plate can only be used for the connection of two circuits and that if two more circuits have to be connected together a second conducting-plate has to be brought into use. To connect this second conducting-plate, it is necessary that the plugs to be used for this connection should have their contactpoints located at a place where they can strike the second conducting-plate, and if a third connection should be necessary before the lirst two connections are broken it is necessary to use plugs the contact-points of which are located at a place where they can strike the third conducting-plate, and so on, till the whole series of conducting-plates is brought into use. Thisv arrangement necessitates, first, that there should be two plugs having' their contact-points in like place; second, that. the contact-points of each pair ofl plugs should differ in'location from thelocation of the contact-points of the other pairs of plugs.

In our case, where the switchboard is provided with from twenty to thirty conductingplates, the operator has to be provided with from twenty to thirty pairs of plugs, and to distinguish each pair from the others I have, as set forth in the description of the drawings, provided each pair of plugs with a different letter of the alphabet.

In telephony the connection between two circuits has mostly to be made if one circuit is calling and asks to be connected to a second circuit. The calling subscriber has closed the circuit which connects him with the common source of electricity and is awaiting development. The circuit to be connected to the calling-circuit has first to be called up, and if all the operations should be performed only through the insertion of two plugs it is obvious that the plug inthe hole of the circuit to be called has to perform a function Awhich the plug inserted in the hole of the circuit calling does not need to perform. The action and therefore the construction of the two plugs of one pair differ from each other, and I have provided one series of plugs with the devices, circuits, and connections as necessary to be used for the calling-circuit, and I provide one series of plugs with the devices, circuits, and connections necessary to be used for the called-up circuit. I/Ve therefore have twenty or thirty plugs to be used, one for the calling-circuits and twenty or thirty plugs to be used only for the circuits to be called.

I have at the beginning' of the description stated that the calling-up series should be distinguished from the other series by the color of the plug. If we make the color of the calling-plugs white and the color of the to-becalled plugs red and use the letters of the alphabet for each pair, then we have plugs colored White lettered "A B C D, &c., and red plugs lettered A B C 1), &c. The plugs should have a receptacle or stand, and it is best that this receptacle or stand should be so arranged that each plug would glow if put in its proper place. This part of the arrangement I have not described and do not claim, as this will form the subject-matter of' another application. It is now assumed that the exchange is equipped with the devices as enumerated. On desk No. 3, the operator of which has circuits from No. 601 to 900, inclusive, in charge, the desk-lamp of No. 602

glows. ,The operator of desk No. 3, places 2 the plug' of the calling-circuit in the hole No.

602 and inquires what 602 wants. If 704 is wanted, the operator first looks at the-lightbearing the same letter as the plug already inserted in the hole of No. 704. As'soon asthe lamps in these two plugs` will cease to light he removes and replaces the same again in the receptacle or stand.

Having now described my invention, what Iclaim as new, and desire to secure by Letters Patent, is-

l. In combination, a telephonie distributing-board, line-terminals in each board, fixed conductors having parts adjacent to each of said terminals, and plugs for said board, said plugs provided with electromagnetic devices and means toV engage in one or the other of said fixed conductors, said plugs also provided with an annunciating device.

2. A telephonie switchboard consisting of the following instrumentalities: a face-plate provided for each of the circuits connected to said switchboard with a series of contactpoints, one contact point connected to a grounded source of electricity, one contactpoint connected to a pole of a source of electricity not grounded, one contact-point connected to one terminal of the operators phone and one contact-point connected to the second pole of the source of electricity not grounded, in combination with rear plate or plates provided with contacts for each ofthe circuits connected to said board.

3. A switchboard embracing a face-plate provided for each of the circuits connected to said switchboard with five contact-points in combination with plugs for said board adapted to. coact with said contact-points if inserted in their place.

4. In combination, a telephonie switchboard and plugs for said switchboard, each of said plugs provided with an electromagnetic device, an annunciating-lamp and means to connect with one or the other of the contacts With which said board is provided.

A telephonie switchboard embracing a non-conducting face-plate, a series of intervening conducting plates or strips and a nonconducting rear plate, the face-plate as Well as the rear plate provided with contacts adapted to coact with the contacts of the plugs when inserted in combination with plugs provided with contacts and electromagnetic means.

6. A telephonie switchboard embracing the following instrumentalities: a face-plate provided with a series of contacts for each of the circuits connected to said board, a series of stationary conducting-plates and a rear plate provided for each of the circuits with a series of contacts, a series of plugs for said switchboard, each plug adapted to coact with onel or TOO the other of said contacts when placed in pos1t1on, cach ot' said plug's containing' electromag'netic means and means to annunclatc the condition of the circuit with which said plug' connecting' means outside of said conducting'- plates, a series ot' plugs adapted to coact with one or the other of said connecting' means when placed in position, each plug' provided also with electromagnetic means and a visible signal adapted to indicate the condition of the circuit to which said plug' pertains.

ln testimony whereof l hereby sign my name, in the presence of two subscribing' witnesses, this 22d day of November, A. D. 1900.

ISIDOR KITSEE.

lVitnesses:

EDITH R. STILLEY, CHAs. KRIssENBUcH. 

